One type of trim strip used on automobile bodies for decorative and bump protection purposes consists of a long, narrow thermoplastic strip which may be either partially or entirely covered with a thin outer layer of a chrome-appearing plastic film. By way of example, such strips may extend the length of the body of an automobile along the sides thereof and formed in sections to accomodate the doors, etc. Such strips may be fastened to the automotive body either by an appropriate adhesive or by mechanical fastening clips or screws.
For decorative purposes, usually one and sometimes both opposite ends of such a long strip is formed with a pointed or spear-like end. To form such end, a V-shaped notch has been formed in the end of the strip, the walls of the notch have been coated with a suitable adhesive and thereafter, the walls bent towards each other and held until setting of the adhesive.
Another type of trim strip, used for example on the side body panels of stationwagons, is likewise formed of a thin thermoplastic material, either with or without chrome-like films applied thereto for decorative purposes, with these strips being wider than the above-mentioned strips and being formed like picture frames, to give a four-sided arrangement. In the past, this type of trim strip has been assembled into the picture frame relationship by cutting their opposite ends at angles and abutting them against adjacent-angled ends of strips and securing these together by adhesive to form a miter joint.
The manufacture of the spear-end and the mitered corner joints of both of the above types of trim strips has been a relatively inefficient, slow process which, quite frequently, has resulted in poor, i.e., unacceptable quality, joints.
Thus, this invention relates to a process and apparatus for forming such type joints in plastic strips, which eliminates the use of adhesives and produces a far better quality joint more rapidly and at lower cost. While the invention focuses on trim strips, it may also be applied to similar strips used for other purposes.